The present invention relates to a heat exchanger constituting part of the freezing cycle in an air-conditioning system installed in a vehicle.
Heat exchangers of this type in the prior art include the laminated heat exchanger disclosed in Japanese Unexamined Utility Model Publication No. H 7-12778, which is achieved by laminating a pair of upper header portions, i.e., an upper front header portion and an upper rear header portion formed at one end in the lengthwise direction, a pair of lower header portions, i.e., a lower front header portion and a lower rear header portion formed at the other end along the lengthwise direction and a middle plate having flat tubes individually communicating between the upper front and upper rear header portions and the lower front and lower rear header portions via fins. In addition, a pair of upper tank groups constituted by laminating the upper front and upper rear header portions are each partitioned at an approximate center to be divided into two tank blocks. A pair of lower tank groups are constituted by laminating the lower front and lower rear header portions.
In the laminated heat exchanger with individual tank blocks formed by dividing the upper tank groups referred to as a first upper front tank block, a second upper front tank block, a first upper rear tank block and a second upper rear tank block, coolant enters the first upper front tank block through a fluid induction port, travels downward through the flat tubes to enter the lower front tank group and then travels upward through the flat tubes from the lower front tank group to enter the second upper front tank block. Next, the coolant bypasses a communicating portion 21 before entering the second upper rear tank block then enters the lower rear tank group by traveling downward through the flat tube from the second upper rear tank block, travels through the lower rear tank group and then moves upward through the flat tubes before flowing into the first upper rear tank block to flow out through a fluid discharge port.
However, in the heat exchanger in the prior art structured as described above, in which the coolant having flowed into the first upper front tank block travels down through the flat tubes to flow into the lower front tank group, travels through the lower front tank group and moves upward through the flat tube to reach the second upper front tank block, the quantity of coolant moving upward through the flat tubes located near the partitions is smaller than the quantity of coolant in other areas, resulting in the coolant temperature in this area rising higher. Likewise, the quantity of coolant traveling upward through the flat tubes located near the partitions is smaller than the quantity of coolant in other areas with regard to the coolant that travels downward from the second upper rear tank block to the lower rear tank group and moves through the lower rear tank group to travel upward to the first upper rear tank block resulting in the temperature in this area rising higher.
As described above, due to the reduction in the quantity of coolant near the partitions causing an increase in the temperature, a problem arises in that the temperature distribution in the vicinity of the center of the heat exchanger where the airflow quantity is most stable, becomes very poor. In particular, if the width of the heat exchanger itself is reduced to satisfy the increasing need for further miniaturization of the heat exchanger to be fitted inside a more compact air conditioning system, which, in turn, must be installed in reduced available space inside a vehicle, a deterioration in the temperature distribution in the vicinity of the center, which results in a great reduction in the heat exchanging capability, poses a serious problem.
Accordingly, an object of the present invention is to provide a thinner heat exchanger with good temperature distribution and high heat exchanging capability.
In order to achieve the object described above, the laminated heat exchanger according to the present invention comprising a plurality of tube elements each having a pair of one-end tank portions provided at one end in the lengthwise direction and a pair of other-end tank portions provided at the other end along the lengthwise direction, a first coolant passage communicating between one of the one-end tank portions and one of the other-end tank portions and a second coolant passage communicating between the other one-end tank portion and the other other-end tank portion and fins provided between the tube elements, is further provided with a first tank group constituted of tank portions in individual one-end tank portion pairs on one side that are in communication with each other along the laminating direction, which communicates with a coolant intake, a second tank group constituted of tank portions in the individual other-end tank portion pairs on one side that are in communication with each other along the laminating direction, a third tank group constituted of tank portions in the other-end tank portion pairs on the other side that are in communication with each other along the laminating direction, a fourth tank group constituted of tank portions in the one end tank portion pairs on the other side that are in communication with each other along the laminating direction, which communicate with a coolant outlet, a bypass passage communicating between the second tank group and the third tank group, a first path comprising a first coolant passage group constituted of the first coolant passages and extending from the first tank group to the second tank group and a second path comprising a second coolant passage group constituted of the second coolant passages and extending from the third tank group to the fourth tank group.
By adopting the structure described above, a two-path heat exchanger having the first path through which the coolant travels from the first tank group to the second tank group and the second path through which the coolant travels from the third tank group to the fourth tank group, in which the coolant flows in different directions in the first path and the second path, is achieved. Thus, the area over which the temperature rises high in the first path and the area over which the temperature is low in the second path are aligned relative to the direction of airflow and the area in which the temperature rises high in the second path and the area over which the temperature is low in the first path are aligned relative to the direction of airflow to improve the temperature distribution in the heat exchanger.
In addition, according to the present invention, it is desirable that the width of the tube elements along the direction of airflow be set in a range of 30-57 mm. It has been confirmed through testing that the heat exchanger structured as described above is capable of sustaining full heat exchanging capability with the width set within this range.